PM Update: A tale of two air masses today, but summerlike tomorrow

5:50 p.m.: A few isolated showers and storms have popped up, mainly to the northwest of the area, but including places like Loudoun County. This activity is riding along the front draped across the area, and most of it is pulsing up and down rather quickly. However, the odds of a storm have probably increased at least a bit since the original time of this post. The Storm Prediction Center is monitoring places mainly north and west, but also locally, for a potential thunderstorm watch.

4:30 p.m.: One of the main things I noticed about today was humidity—guess it’s that time of year. Variably cloudy skies, and a front draped across the area, led to a wide range of temperatures. Highs have only hit the 60s to the north and east, while they’re past 80 to the south and west. In the middle, D.C. has reached the 70s. So far, the risk of storms seems subdued compared to potential, and it’s possible we’ll make it through the daylight hours without much of note.

Through Tonight: It stays slightly muggy through the night (and beyond), so we’re not going to get too cool out there. In addition to mostly cloudy skies and the slight risk of a shower or thunderstorm early, we’ll need to watch for another line of showers/storms after midnight. Indications are it’ll also be hard pressed to make it through here in any significant fashion. Lows dip to the upper 50s and lower 60s.

Tomorrow (Thursday): Partly sunny skies invigorate this warm air mass, sending highs back well above normal, and it should feel pretty summerlike! There’s an outside risk of an isolated shower or storm during the day, but it’s a very low one. Otherwise, soak up those rays (with sunscreen, of course) in temperatures rising to about the mid-80s.

New model: NOAA has unveiled a new short-term model called Rapid Refresh (RAP). It updates every hour and forecasts out to 18 hours. The new model, tested for 22 months before going into service, will replace the Rapid Update Cycle (RUC) model. In comparisons, the RAP has outperformed the RUC and scientists are quite excited about its capability to forecast severe weather.

Pollen: Susan Kosisky of the US Army Centralized Allergen Extract Lab writes, “Tree pollen is in the HIGH range at 211.18 gr/cubic meter Grass pollen is MODERATE (NAB range) at 7.35 gr/cubic meter, which is high for local area grass counts Weed pollen is LOW at 1.28 gr/cubic meter Mold spores remain LOW at 6258.83 spores/cubic meter.”

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